1. Field of the Invention
The present invention relates to a crimped terminal attached aluminum electric wire. In the present specification, both an electric wire made of aluminum and an electric wire made of aluminum alloy are named an aluminum electric wire.
2. Description of the Related Art
Typically, copper electric wires are used for wire harnesses that are wired in a vehicle such as an automobile. When these wire harnesses are connected or the wire harness and an in-vehicle apparatus are connected, a terminal is attached to the copper electric wire of the wire harness, and this kind of terminal is typically attached to the copper electric wire by being crimped.
Typically, the terminal, which is crimped to the copper electric wire, includes a bottom plate on which a conductor part of the copper electric wire which is formed by twisting a plurality of copper strands is placed, and a pair of conductor tightening pieces which are provided adjacently to the bottom plate to hold the conductor part which is placed on the bottom plate. When the pair of conductor tightening pieces are crimped inward, the conductor part of the copper electric wire is sandwiched between the bottom plate and the pair of conductor tightening pieces so that the terminal is crimped to the conductor part of the copper electric wire by this sandwiching.
In recent years, in consideration of the lightweighting of vehicles, and the easiness of material recycling, in addition to the lack of copper resource, it is considered to use aluminum electric wires to replace the copper electric wires. However, an oxide film formed on the surface of aluminum is thicker than that of copper, and for the aluminum electric wire, the contact resistance between the conductor part and the crimped terminal tends to become relatively higher.
Thus, to reduce the contact resistance between the conductor part of the aluminum electric wire and the crimped terminal, a method is adopted to strongly crimp a barrel (conductor crimping part) of the crimped terminal to the conductor part of the aluminum electric wire to raise compression rate of the conductor part of the aluminum electric wire. When this method is used, because the conductor part of the aluminum electric wire is strongly crimped, the oxide film of the strands of the conductor part of the aluminum electric wire is broken and the contact resistance between the conductor part and the crimped terminal of the aluminum electric wire is reduced.
It is known that when water exists at the contact part (crimped part) where different kinds of metals (that is, the aluminum material and the copper material) contact, the two metals (aluminum and copper) dissolve into the water as ions, a potential difference between the aluminum material and the copper material is produced, and electrolytic corrosion occurs.
Thus, when the crimped terminal made of copper or copper alloy is connected to the conductor part of the aluminum electric wire, the crimped part of the conductor part of the aluminum electric wire crimped by the barrel of the crimped terminal is crimped at a high compression rate so that water is prevented from invading the contact portion where the conductor part of the aluminum electric wire and the barrel of the crimped terminal contact, and the occurrence of the electrolytic corrosion can be avoided.
However, part of the core line of the conductor part of the aluminum electric wire, which is axially before and after the barrel of the crimped terminal crimped by the barrel of the crimped terminal in the axial direction, contacts the crimped terminal in an exposed state, and when water attaches to this part, the contact portion of the conductor part of the aluminum electric wire and the barrel of the crimped terminal becomes immersed in electrolytic solution, and the electrolytic corrosion which is that metal aluminum whose ionization tendency is high dissolves might advance.
Thus, a crimping structure is proposed in which the conductor part of the aluminum electric wire and a crimped terminal made by copper or copper alloy are connected, and water is prevented from invading the contact portion of the conductor part and the crimped terminal.
In a terminal metal fitting attached electric wire disclosed in a patent document 1, the front ends of conductor tightening pieces of a conductor crimping part in the crimped terminal are provided with bent portions to control the distal end section of the conductor of the electric wire which projects to the front side of the conductor crimping part from jumping up while the conductor tightening pieces are tightened, and anticorrosion material is coated in a range from the conductor exposed at the front side of the conductor crimping part on this bent portions via a joint of the conductor tightening pieces to a joint of coating tightening pieces.
Patent document 1: JP-A-2011-243329